[time-nuts] Pendulums & Atomic Clocks & Gravity

[Ulrich Bangert]

Arnold,

let us make one of the big experiments in physics and switch gravity
off. In the moment that we do so we see the satellite move away along a
straight line which is tangential to earth's surface. That is: Without
the presence of an force the satellite keeps its velocity AND its
direction as Newton's first law says. In a time delta-T it has moved
this tangential line a certain way which clearly depends on its
velocity. Note that it has ALSO moved an certain amount away from
earth's center. Now lets switch gravity on again. If "falling" due to
gravity during the time interval delta-T exactly compensates moving away
from earth due to the tangential movement you get... yes an circular
motion and yes of cource let delta-T go to zero to make it a smooth
motion. Only one force necessary: Gravity. If you are asking for the
gravitational force of the satellite on earth: Yes, it is there and in
reality the satellite does not exactly move around earth but earth and
satellite move around a common center of mass. 

>From the above argument you can easily see why the satellite's
tangential velocity does indeed play an important role in the process
but no centrifugal forces.

Best regards
Ulrich Bangert, DF6JB 

> -----Ursprüngliche Nachricht-----
> Von: time-nuts-bounces at febo.com 
> [mailto:time-nuts-bounces at febo.com] Im Auftrag von Arnold Tibus
> Gesendet: Sonntag, 27. Mai 2007 22:52
> An: Discussion of precise time and frequency measurement
> Betreff: Re: [time-nuts] Pendulums & Atomic Clocks & Gravity
> 
> 
> Hello Ulrich, 
> is it not important to bring into the game the satellite's 
> velocity in 
> relation to earth (on a tangential straight path deviated by 
> gravitational acceleration)? 
> 
> 73,
> Arnold, DK2WT
> 
> 
> 
> On Sun, 27 May 2007 19:59:22 +0200, Ulrich Bangert wrote:
> 
> >Didier,
> 
> >> gravitational forces, so do objects in Lagrange points. 
> These points
> >> represent areas where the centrifugal forces compensate for 
> >> gravity....
> 
> >I am almost sure that this will again produce me a lot of trouble in 
> >answering a lot of people but the idea that there are centrifugal 
> >forces which compensate for gravity are one of the BIGGEST 
> misconcepts 
> >that one may have in physics at all although it is quite 
> common and you 
> >may find statements like that eben in (bad) physics textbooks.
> 
> >Centrifugal forces are so called fictitious forces which are only 
> >observed from within accelerated systems. Normal physics is done in 
> >inertial systems. In an inertial system consisting of earth and an 
> >satellite there are only TWO forces available: The gravity force by 
> >which earth attracts the satellite and the gravitational 
> force by which 
> >the satellite attracts earth. They are of the same magnitude but of 
> >opposite direction. That is the reason why the "sum of 
> forces" is zero 
> >for the closed system consisting of earth and satellite. There is no 
> >place for any other force like centrifugal or so because there is no 
> >counterforce available that would make the sum of forces 
> zero i case a 
> >centrifugal force would exist. In case you like to discuss it a bit 
> >please go on but be prepared that I will to blow your arguments into 
> >little bits. A good idea to start with is to look after what 
> Newton's 
> >first law is saying about the behaviour of a body for which 
> all forces 
> >compensate each other. Is that what a satellite does???
> 
> >73 Ulrich, DF6JB
> 
> >> -----Ursprüngliche Nachricht-----
> >> Von: time-nuts-bounces at febo.com
> >> [mailto:time-nuts-bounces at febo.com] Im Auftrag von Didier Juges
> >> Gesendet: Sonntag, 27. Mai 2007 16:54
> >> An: Discussion of precise time and frequency measurement
> >> Betreff: Re: [time-nuts] Pendulums & Atomic Clocks & Gravity
> >> 
> >> 
> >> For the same reason that a satellite in free fall is still 
> subject to
> >> gravitational forces, so do objects in Lagrange points. 
> These points 
> >> represent areas where the centrifugal forces compensate for 
> >> gravity from 
> >> two objects instead of one for a regular satellite. The only 
> >> way to be 
> >> free from gravitation is infinite distance from mass, 
> until someone 
> >> actually invents the famous gravitational shield :-) I hope 
> >> it comes in 
> >> spray form...
> >> 
> >> Didier
> >> 
> >> Neville Michie wrote:
> >> > Look up Lagrangian points on Wikipedia.
> >> > There are points of zero gravitational force, about our planet. 
> >> > What is more, these points are stationary with respect 
> to Earth, so
> >> > Doppler effects would be zero.
> >> > As the distance from Sun to Earth to Moon varies through 
> >> the year it
> >> > follows that the distance from Earth of these points must
> >> vary on a
> >> > small scale.
> >> > These points are good for satelites as the orbit never decays. 
> >> > cheers, Neville Michie
> >> >
> >> >   
> >> >> _______________________________________________
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> >> >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> 
> 
> 
> 
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